1. Field of the Invention
At least one embodiment of the invention generally relates to implantable medical devices and data communication from implantable medical devices to an external device.
2. Description of the Related Art
Typically, implantable devices, in particular implantable medical devices, such as implantable therapy and/or monitoring devices including pacemakers, cardioverters and defibrillators or the like, may include data communication means to transmit data from the implantable medical device to an external device or vice versa.
A system for data communication with a medical device thus, generally, includes an implantable medical device and an external device such as a programmer.
A typical implantable medical device comprises a battery, a monitoring and/or therapy control unit, in some cases additionally one or more therapy units such as stimulation units and a memory for storing control program and/or data sensed by the implantable medical device. If the implantable medical device is a pacemaker or an implantable cardioverter/defibrillator (ICD), generally, the therapy units comprise stimulation units for generating and delivering electric stimulation pulses to a patient's heart tissue (myocardium).
Generally, in order to transmit data sensed by the implantable medical device to an external device, a telemetry unit may be provided. Typically the telemetry unit may be configured to allow bidirectional data communication, that is, the telemetry unit may transmit and receive data wirelessly.
Limited battery capacity of an implantable medical device generally calls for energy-efficient data communication. An implantable medical device with limited battery power typically requires a low power communication scheme in order to program it and to download acquired data. With extremely low power communication, generally, more data may be transmitted more often.
Typical communication schemes used for data communication by a telemetry unit involve either RF or magnetic communication. Generally, RF frequencies of ˜400 or ˜900 MHz or magnetic coupling in the 100s of kHz range require several mA of current to transmit and receive data. Such high current requirements are typically out of reach of devices with battery capacities of at most a few hundred mAh.
In addition, RF schemes generally require large antennas and magnetic coupling generally requires large transmit and receive coils for communication. The space available in miniaturized implants, typically, would not allow such large coils or antennas.
In view of the above, there is a need for a low power communication scheme that does not employ RF or magnetic coupling.